Cardiovascular related deaths constitute more than 500,000 deaths annually in the U.S. and many more death on a global scale. A significant portion of deaths related to cardiovascular problems are attributed to coronary artery disease. In coronary artery disease, the chief culprit is the build up of plaque, specifically soft-plaque, in the arteries. Accordingly, there is high interest in the medical community in detecting coronary artery disease.
Typically, soft-plaque is not easily detectable in X-ray images or non-contrasted computer tomography (CT) images. In comparison, calcified plaque is much more readily detectable than soft plaque and thus the presence of hard plaque has been used as a surrogate for the presence of soft plaque, with the reasoning being that calcified plaque is the by product of ruptured soft plaque.
Coronary plaque can be classified into six stages according to the Stary scale. According to general medical consensus, detecting the presence of plaque in stage 4 and stage 5 is very important because stages 4 and 5 constitute critical vulnerable plaque which could lead to rupture or dislodging of the plaque causing blockages, which in turn could lead to myocardial infarction (MCI), MCI being commonly known as “heart attack.”
A conventional medical imaging technique for determining plaque and constituency of the plaque is intravascular ultrasound (IVUS). However IVUS is only performed on symptomatic patients due to the invasive nature of IVUS. Symptomatic patients are already at an advanced stage and past non-invasive therapy options.
With the advent of cardiac volume computed tomography (VCT) and the ever increasing spatial and temporal resolution of IVUS and with the impending advent of high definition (HD) VCT, imaging a contrasted study of heat that is gated to mitigate heart motion is within reasonable reach. Using IVUS images and HD VCT images, plaque can be distinguished from lumen and plaque can be distinguished from calcification. However distinguishing plaque from lumen and calcification is still very difficult in an automated manner.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for non-invasive detection of soft coronary plaque at stages earlier than stage 4 and stage 5. There is also a need for improved method of distinguishing plaque from lumen and distinguishing plaque from calcification in an automated manner.